Nebular Versus Parent Body Processing

Brearley, A. J.

doi:10.1016/b978-0-08-095975-7.00106-6

Cited by 59 publications

(73 citation statements)

References 196 publications

(315 reference statements)

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“…When evidence of very limited minor metasomatic effects is observed in a few rare components in an apparently otherwise unaltered chondrite, what does this mean? It could be interpreted as evidence that these components were metasomatized prior to accretion, either in the nebular or some other protoplanetary body, as suggested by Brearley (2003). On the other hand, it may simply be the fact that the glass in this object had a composition that made it much more susceptible to alteration by a metasomatizing fluid of a particular composition.…”

Section: Environment Of Metasomatic Alteration Of Co3 Chondritesmentioning

confidence: 92%

“…A problem unique to chondrites is the issue of the environment where elemental mass transport took place. A long standing debate in the meteoritics literature concerns the question of whether metasomatism occurred when the components of chondrites were free floating in the protoplanetary disk, prior to accretion, or whether metasomatism occurred after these components were assembled together into asteroidal parent bodies (e.g., Krot et al 1995;Brearley 2003). These different environments are commonly referred to as nebular and parent body environments, respectively, but the terms pre-accretionary or post-accretionary processes are also commonly used in the literature.…”

Section: Metasomatism In Chondrites: Unique Samples Unique Problemsmentioning

confidence: 98%

“…As discussed by Brearley (2003), potential indicators of nebular alteration of chondritic components are variability in the style and extent of alteration effects between components with similar compositional and mineralogical characteristics. Heterogeneity in the extent of alteration has to be interpreted with caution, as discussed above.…”

Section: Evidence Of Nebular Metasomatic Alteration Of Co Chondritesmentioning

confidence: 98%

“…We evaluate the evidence for these different scenarios below. Brearley (2003) discussed possible mineralogical, compositional, and isotopic criteria that might be used to differentiate between alteration processes (aqueous alteration and metasomatism) that occurred either prior to or post accretion of asteroidal parent bodies. The complexity and diversity of chondritic components essential precludes any single criterion as being uniquely indicative of one environment versus another.…”

Section: Environment Of Metasomatic Alteration Of Co3 Chondritesmentioning

confidence: 99%

“…Chondrites are rocks that represent lithified samples of materials that originate from small asteroidal bodies from within the main Asteroid belt~3 AU (astronomical units) from the Sun. Although some of the secondary processing of chondritic meteorites may have occurred prior to formation (accretion) of these asteroidal parent bodies (e.g., Bischoff 1998;Brearley 2003), much of the evidence indicates that this processing occurred largely after accretion. Our ability to use meteorites to provide us with information about the stage of solar system evolution prior to the formation of planetary bodies requires a comprehensive understanding of how secondary processes may have affected this primary record.…”

Section: Introductionmentioning

confidence: 98%

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Metasomatism in the Early Solar System: The Record from Chondritic Meteorites

Brearley

Krot

2012

Lecture Notes in Earth System Sciences

103

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Mineralogic, petrologic, and isotopic studies of chondritic meteorites have revealed a significant body of evidence of metasomatic processes during the earliest stages of Solar System evolution. The exact nature of these processes, as well as the conditions and environments where metasomatism occurred, are still the subject of vigorous debate. The interaction of aqueous fluids with early Solar System solids affected different chondrite groups to different degrees: even within a single chondrite group the effects of metasomatism can be highly variable. Among the carbonaceous chondrite groups, the CV (Vigarano-type) and CO (Ornans-type) chondrites show the best documented evidence of metasomatic effects. In the oxidized subgroup of the CV chondrites, Ca-Al-rich Inclusions (CAIs), Amoeboid Olivine Aggregates (AOAs), chondrules, and matrix have all been extensively affected by Fe-alkali-halogen metasomatism, that has resulted in the formation of a wide range of secondary, dominantly anhydrous minerals, including grossular, andradite, wollastonite, monticellite, anorthite, forsterite, ferroan olivine, corundum, Na-melilite, nepheline, sodalite, wadalite, Al-diopside, kushiroite, ferroan diopside À hedenbergite pyroxenes, ilmenite, phosphates, magnetite, awaruite, tetrataenite, and Fe,Ni sulfides. Hydrous phases are much rarer, but include, margarite, vesuvianite, and kaolinite. The mineral assemblages that form are highly dependent on the primary mineralogy of the host object: distinct mineral assemblages are produced by alteration of CAIs, chondrules, and matrix, for example. Nebular and asteroidal scenarios for these metasomatic effects have been extensively discussed in the literature for the metasomatism observed in the

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Section: Environment Of Metasomatic Alteration Of Co3 Chondritesmentioning

confidence: 92%

Section: Metasomatism In Chondrites: Unique Samples Unique Problemsmentioning

confidence: 98%

Section: Evidence Of Nebular Metasomatic Alteration Of Co Chondritesmentioning

confidence: 98%

Section: Environment Of Metasomatic Alteration Of Co3 Chondritesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

See 3 more Smart Citations

Metasomatism in the Early Solar System: The Record from Chondritic Meteorites

Brearley

Krot

2012

Lecture Notes in Earth System Sciences

103

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An impact origin for hydrated silicates on Mars: A synthesis

et al. 2013

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[1] Recent Mars-orbiting spectrometers continue to detect surface materials containing hydrated silicates, particularly clays and amorphous phases (e.g., silica glasses), concentrated within the heavily cratered Noachian highlands crust. This paper provides a review, summary, and synthesis of observations from terrestrial impact structures with current Martian data. It is suggested that numerous and frequent impacts into the volatile-rich silicate crust of Mars, through direct and indirect impact-generated mechanisms, represent a plausible hypothesis that can explain the widespread distribution of hydrated silicates in the surface and subsurface of the heavily cratered Noachian highlands crust largely independent of climate. In addition to impact-generated hydrothermal activity, devitrification, autometamorphism, and the voluminous production of impact "damaged" materials that are susceptible to alteration must be considered. When taken together, a drastically different early climate on Mars, in which water is stable at the surface for extended periods of time, cannot be ruled out; however, it is noted here that these additional impact mechanisms can operate and thereby extend the range of possible alteration settings to include climate conditions that may have been predominately colder and drier. Such a climate would not be dissimilar to the conditions of today, with the important exceptions of a higher geothermal gradient, and punctuated thermal disturbance to the cryosphere and hydrosphere from igneous activity and an exponentially higher impact flux.

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